【判断题】由无缝钢管制成的一搅拌轴,外径D=89mm、壁厚d=5mm,材料为20号钢,使用时的最大扭矩T=1930N·m, .校核此轴的强度。 结论:最大剪应力小于许用剪应力,强度满足条件。
【单选题】To trade with the third world is mainly because that it is full of natural resources.
【简答题】Forms of compensation trade mainly include ______ and counter purchase.